Method of manufacturing electronic tubes



Filed July 6, 1940 Fig 3 Fig. 2

1 3 HZHQ2H o 0 5 2 4H2 2 F fl V fl w 158L2 1 92 122 Patented Nov. 17,1942 METHOD OF MANUFACTURING ELECTRONIC TUBES Peter-Paul Fries, Berlin,Germany; vested in the Alien Property Custodian Application July 6,1940, Serial No. 344,295 In Germany September 1, 1939 4 Claims.

The present invention relates to the manufacture of electronic tubesconsisting of a base supporting the electrodes and a cover, both made ofa ceramic material (like porcelain or glass) and being assembled by aseal of melted glass enamel.

In carrying out this process a difliculty arises by the fact that byheating the tube in free air or in an oxidising atmosphere theelectrodes are damaged while in a neutral or reducing atmosphere theenamel is reduced and loses its solidity.

It is the object of the present invention to overcome the abovedifiiculty by keeping, during the time the tube is heated for meltingthe enamel, the outside of the tube in an oxidising, its inside in areducing atmosphere.

In the accompanying drawing Fig. 1 is a longitudinal section of a tubeaccording to the invention, whilst Fig. 2 shows a cross-section and Fig.3 a longitudinal section of a furnace as used for carrying out theinvention.

Referring to Fig. 1, l I is the base carrying the electrode system H,sealed leads-in I3 and I6 and the exhaust tube [5. A circular groove llof the base is filled with enamel (flint glass) which is preferablymelted down before the electrode system is mounted. The edge of thecover 12 fits the groove. In order to assemble base and cover the tubeis entirely heated until the enamel is melted. According to theinvention during l8 which is introduced through the exhaust tube I5.

The protective gas consists preferably of nitrogen which is carefullyfreed from oxygen and is mixed with a few percents of hydrogen.

For manufacturing such tubes in bulk according to the invention twodifferent ways are practicable.

The simplest Way is to provide several furnaces each of which is chargedwith a large number of tubes, in each tube being introduced a tubule I8for leading in the protective gas. Each furnace is slowly heated andkept hot until the enamel is melted, and then cooled down slowly inorder to avoid cracking of the tubes. The furnaces are operated atdifferent phases so that one furnace may be charged and then another onebe discharged whilst the remaining ones are in the heating or coolingperiod. Thus the heating energy as well as the manipulation are equallydistributed over the time.

The second way consists in using an elongated fumace through which thetubes are conveyed by a metal belt conducted with slow speed along thefurnace. In Figs. 2 and 3 2B is the furnace, 2| the belt, l2 one of thetubes and IS the tubule for blowing in the protecting gas. These tubulesare fixed on a second belt 23 which moves in a channel 22 at the samespeed as 2| and tightens the longitudinal slit of channel 22. Thechannel is filled with said gas under moderate pressure which penetratesinto the tubes thru the tubules 18 whilst the outside of the tubes is infree air.

I claim:

1. A method of manufacturing an electronic tube consisting of a basecarrying the electrodes and a cover, both made of insulating material,comprising the steps of filling an annular groove in the upper side ofsaid base with enamel, putting said cover upon said base whereby theedge of said cover fits said groove, conducting into said tube a streamof a gas protecting said electrodes against oxidation whilst the outsideof said tube is kept in an oxidising atmosphere, and heating said tubeuntil base and cover are sealed by the melted enamel, said gas beingconducted into the tube by means of a fine tubule introduced through thepump shaft of said base.

2. A method of manufacturing electronic tubes each consisting of a basecarrying the electrodes and a cover, both made of insulating material,comprising the steps of filling an annular groove in the upper side ofsaid base with enamel, putting said cover upon said base whereby theedge of said cover fits said groove, conducting into said tube a streamof a gas protecting said electrodes against oxidation whilst the outsideof said tube is kept in an oxidising atmosphere, and heating said tubeuntil base and cover are sealed by the melted enamel, said gas beingconducted into the tube by means of a fine tubule introduced through thepump shaft of said base, said heating being executed by putting a seriesof said tubes over said tubules, said tubules being supported by anendless metallic strip moving through a heated furnace, whilst saidprotection gas is led to said tubules by means of a channel placed belowsaid furnace.

3. A method of manufacturing electronic tubes each consisting of a basecarrying the electrodes and a cover, both made of insulating material,comprising the steps of filling an annular groove in the upper side ofsaid base with enamel, putting said cover upon said base whereby theedge of said cover fits said groove, conducting through said tube astream of a gas protecting said'electrodes against oxidation whilst theoutside of said tube is kept in an oxidising atmosphere, and heatingsaid tube until base and cover are sealed by the melted enamel, said gasbeing conducted into the tube by means of a fine tubule introducedthrough the pump shaft of said base, said heating being executed byputting a series of said tubes over said tubules, said tubules beingsupported by an endless metallic strip moving through a heated furnace,whilst said protecting gas is led to said tubules by means of a channelplaced below said furnace, only the middle part of said furnace beingheated.

4. A method of manufacturing electronic tubes each consisting of a basecarrying the electrodes and a cover, both made of'insulating material,

comprising the steps of filling an annular'groove said heating beingexecuted by placing a large number of such tubes into one of severalfurnaces and heating and cooling said furnace slowly in difierentphases.

PETER-PAUL FRIES.

